Charles s



c. s. DEMAREST. TELEPHONEREPEA TER EQUIPMENT.

APPLICATION FILED MAY 9. i919.

Patented Aug. 2; 1921.

WEB YER SHUNT INVENTOR ficfiflemasrl ATTORNEY transmission line in orderto preventthe repeaters.

1 lii R fis MA ES .OF'BROOKLYNQ New Year, ss ca o answer PHONE AnnTELEGRAPH COMPANY, n conronarion or NEW-$03K,

'rnnnrnonn nnrnaf'r'nn EQU'IPMENT.

To all whom it may concern:

Be it known'that I, CHARLns S. DEMAREST,"

residing at Brooklyn, in the countvof Kings and State of New York, haveinvented certain Improvements in Telephone Repeater Equipments, of whichthe following is a specification.

This invention relates to transmission cir-' cults which includerepeaters and more particularlyto a means for testing such re- When atransmission line includes repeater apparatus it is customary toassociate withthe repeater artificial lines'or net works suitable forbalancing the sections of the peater from singinnx To test thetransmission gain due to the repeater, the repeater apparatus includingthe artificial lines is disconnected from the transmission line andconnected to a standard form of testing apparatus. This testingapparatus will have .a constant impedance which in all probability willnot-be the same as that of are interconnected by the repeater 'appara-'tus. Accordingly when the testing apparatus is connected to therepeater, the artificial lines will not balance the testing apparatus a.

and will nolonger maintain the repeater in ajbalanced condition andsinging in the repeater will result. 7

It, is an object of the invention to avoid or obviate the abovedescribed difficulties when testingrepeater apparatus and accordingly,the said invention provides testing apparatus'which may be associatedwith rewith the switching means, whereby the repeaters are disconnectedfrom the transmission line and connected to the testing apparatus, meansfor disconnectingfrom the repeaters the balanoingartificial linesnormally associated with the repeaters and for associating with therepeaters artificial lines suitable for balancing the testing apparatus.

and drawing of the invention;

' i In the drawing is illustrated a preferred form of the arrangementsembodying this in.-

wvention. The two sections L and L of a transmission line are showninterconnected Specification of Letters Patent. Patented Aug. 2, 192 1.Application filed May 9, 1919. Serial Nb. 295,912. i

by repeater apparatus. The repeater appa ratus includes the repeaterelements R and R, which are shown as of the mechanical type, althoughany other type, such asthe well known vacuum tube repeater, may beemployed. Normally associated with there-' peater apparatus are the networks N and N adapted for balancing the sections L and L respectively ofthe transmission line, in order I to prevent the repeater from singing.Associated with sections'L and L of the line are the jacks J and J Whenthe plugs P and P of patching cords are inserted in the jacks J and Jrespectively, the repeater apparatus may be disconnected from the lineand connected with the testing apparatus. The patching cords areassociated with the testing apparatus by means of the jacks J and J Whenthe repeater apparatus is disconnected from sections L and L of theline, the net worksN and N are disconnected from the repeater apparatusand the" net works N and N 4 are connected to the repeater apparatus.The net works N and N are of a value suitable for balancing theimpedance of the testing ap paratus. Associated with the jacks J, and

J 4 of the testing apparatus are conductors 12 and 13, respectively.Included in these conductors are the-net works N and N which are of avalue adopted as a standard for purposes of comparison and testing. Theconductors l2 and 13 are normally associated with the contacts of thekey K When the key K is operated, the generatingapparatus 35 which isadapted to generate currents suitable for testing purposes, such, forexample, as currents of telephonic frequency, will be started inoperation. Testing current may then be applied either over condu'ctors12, through the repeater apparatus and over conductors 13, to thereceiver shunt 31 and the operators telephone set 32, or

from the generating apparatus 35 over conductors 13, through therepeater apparatus :and overcondu'ctors 12 to the receiver shunt 31 andthe telephone receiver 32. A keyK is provided in the testing apparatusupon the operation of :which the testing current may be transmitted fromthe generating apparatus 35 through the net work N and tothe telephonereceiver 32. By means of comparing the transmission efliciency, asindicated by a scale on the receiver shunt appa ratus, between thecircuitincluding the net work N, and the circuitincluding the re-'peater apparatus, ameans is afforded for measuring thegain intransmission over a circuit due to the includlng thereln of the re eaterapparatus.

, he operation of the invention is as fol lows: V transmlsslon due tothe includlng 1n the l ne If it is desired to test the gain in of therepeaters R, and R the plugs P and P areinserted, in the jacks J and Jand connected with the section L of the line over the make contacts ofjacks J and J and over conductors 3 and 4. 'When the V =ment1oned crcuit as the operatlon of key K,

plugs P, and P are inserted in the jacks ,J and. J the following circuitis closed:

from ground, sleeve contacts of jack J and plug P sleeve conductors ofthe patchlng cord, sleeve contacts of plug P and jack J,,

I sleeve conductors of jack J over conductor 516, winding of relay 1, tobattery and.

ground, The closing of this circuit will 0perate the relay 1 which willpull up its armatures and will disconnect from the repeater R, the netWork N,, which is normally connected thereto, and will connect the netWork N, over conductors 10, contacts of relay 1 .andover conductors 6 tothe windings of the usual transformer 5 of the repeater apparatus. Whenthe-plugs P and P, are 1n- 4 serted in the jacks J 3 and J respectively,

the following circuit is closed: from ground,

T sleeve contacts of jacks J and plug P sleeve conductors of thepatching cord, sleeve v contacts of plug P and jack J over the sleeveconductors of jack J 3 and over conductor 47, winding of relay 2, tobattery and ground. The closing of. this circuit will energize relay 2which will pull up its armatures and disconnect from the repeater R thenet workNj which is normally connected thereto and will connect the network N over conductors 11, contacts of relay 2, andoverconductors 7, tothe windings of the usual transformer 45 associated with the repeaterapparatus. The keys K and K will now be thrown. The operation of the keyK, closes the following circuit: from ground, make contact of key Kconductor tion of the key K, will close the following circuit: fromground, upper make contact.

of key K conductor 18, winding of relay '17, to battery and ground. Theoperation of key K will also close the following circuit: from ground,lowermake contact of (key K conductor 19, winding of relay 16,

' to battery and ground. The closing of these two last mentionedcircuits will operate the relays 16 and 17. WVhen the generating ap-'paratus 35 is Started in operation and when the relays 16' and 17 areoperated, testing current will be applied from the generating Vapparatus 35 over the following circuit, the 7 key K, being thrown tothe left: over con ductors 22, over conductors 61, left hand makecontacts of key K over conductors 20, contacts and armatures of relay16, over conductors 14, net work N, over conductors 15, armatures andcontacts of relay 17, over conductors 21, right hand'normal contacts ofkeyK over conductors 25 and 26,. from conductor-25 to the receiver 32,and from conductor26, over conductor 28, make con-' tact of key K overconductor 27, to the reso 7 ceiver 32. It is pointed out that thereceiver shunt 31 is not included in this last closesthe short-circuitabout the series resistance 34 and opens the path including the shuntresistance 33. By-means ofthe re ceiver 32, the volume ofthe soundtransmittedv over this last mentioned circuit may be observed. The keyIt, will now be restored to normal. The testing current from thegenerating'apparatus 35 will now be transmitted over the followingcircuit from the generating apparatus 35, over conductors 22, overconductors 61, left hand make con-V tacts of key K over conductors 2'0,net'95 work N over conductors12, tip contacts of jack J 2 and plug P tipconductors of patching cord, tip contacts of plug P andjack J throughthe repeater apparatus in the usual manner, to the tip contacts of j ackJ and plug P over thetipconductors of the patching'cord, tip contacts ofplug P and jack J over conductors 13, net work N normal contacts ofrelay 17, conductors'21, right hand normal contacts of key K overconductors 25 and 26, through the receiver shunt 31, to the telephonereceiver 32. By now adjusting the receiver shunt until the same tone isheard in the receiver as in the' case of the formerly traced circuitthrough the net work N it will be possible to ob-. serve and measurefrom the graduated scale on the receiver shunt the gain due to theincluding in the circuit of the repeater apparatus. By throwing the keyK in the opposite direction, a testing current may be transmittedthrough the repeater apparatus in the opposite direction. By this :meansthe gain in transmission over the transmission line in either direction,due to the repeater apparatus, may be observed and measured. As has beenpreviously pointed out,

the net works N and N which are associ-. ated with the repeaterapparatus, when the testing apparatus is associated therewith, areadapted for balancing the impedance of the testing apparatus and acondition of balance in the repeater apparatus Willbe maintained withrespect to thetesting apparatuswhen the testing apparatus is connectedthereto.

Accordingly, the transmission of testing current from the testingapparatus through the repeater apparatus will not cause fsinging to takeplace in the repeater apparatus.

While the invention has been disclosed as embodied in certain specificarrangements which have been deemed desirable, it is understood that itis capable of embodiment in many and widely varied forms withoutdeparting from the spirit of the invention as defined in the appendedclaims.

What is claimed is:

1. A transmission circuit including lines interconnected by repeaterapparatus, networks normally connected to said repeater apparatus forbalancing said lines, apparatus for testing said repeater apparatus,networks associated with said repeater apparatus for balancing saidtesting apparatus, and means responding when said testing apparatus isconnected to said repeater apparatus for disconnecting said firstmentioned networks from said repeater apparatus and for connecting saidsecond mentioned networks thereto.

2. A transmission circuit including lines interconnected by a telephonerepeater, networks normally connected to said repeater for balancingsaid lines, apparatus for testing said repeater, networks associatedwith said repeater for balancing sa1d testing apparatus, switching meansassociated with said lines and said testing apparatus, means controlledby said switching means for disconnecting said repeater from said linesand for interconnecting said lines over auxiliary conductors, and -meanscontrolled by said switching means for disconnecting said firstmentioned networks from said repeater and for connecting said secondmentioned networks thereto.

3. A transmission circuit including lines interconnected by a telephonerepeater, networks normally connected to said repeater for balancingsaid lines, apparatus for testing said repeater, networks associatedwith said repeater for balancing saidtesting apparatus, jacks associatedwith said lines and said testing apparatus, patching cords adapted tocooperate with said jacks and connect said testing apparatus with saidrepeater, relay means associated with the jacks of said lines andresponding when said testing apparatus is connected to said repeaterfor.

disconnecting said first mentioned networks from said repeater and forconnecting said second mentioned networks thereto.

In testimony whereof I have signed my name to this specification this5th day of May, 1919.

CHARLES S. DEMAREST.

